Genus: "Rhizome subterranean; flowering culms of few
internodes, tall; leaf-blades nearly all arising from near the base of
the culm, very long, erect; inflorescence a much branched panicle, its
branches ascending close to the main axis, the whole compact and cylindric at
flowering; branchlets not jointed, spikelets paired or solitary,
all alike, bisexual, if paired pedicels unequal, and bearing a few long fine
hairs near the thickened top and many fine spreading white hairs also on the
base of the spikelets, hairs twice as long as the glumes or more; glumes
about equal, hairy on the back, thin; lower floret neuter, lemma much
smaller than the glumes, no palea; upper floret hermaphrodite, lemma
thin, not awned, palea present."

Habitat/ecology: A common weed (C4 plant) in hot climatic conditions in several countries of Africa south of Sahara, South and South-east Asia. "Cogon grass invades a wide variety of natural habitats such as desert dunes, wetlands, savannahs and forests, where it out-competes wild plants..." (Randall & Marinelli, 1996; p. 149).
"Its habitat includes the dry sand dunes of shores and deserts as well as swamps
and river margins. It grows in grasslands, in cultivated annual crops, and
on plantations. It quickly enters abandoned farmlands, and it may be seen
on railroad and highway embankments and on both deforested and reforested areas.
It can withstand long dry spells on light soils and will tolerate waterlogging
on heavy soils. It becomes established most quickly on medium to good
soils and is less frequently a pest on poor soils. Although sometimes
reported to be a weed of poor soils, it probably inhabits these areas because of
lack of competition from better grasses which cannot be supported there.
The species makes it maximum development in wet areas of good soils. If
all other factors of the environment are suitable, it can occupy any soil type
where sufficient moisture exists to support growth. The plant grows at
altitudes to 2,000 m in several parts of the world and to 2,700 m in Indonesia"
(Holm et al., 1977; p. 64).

"Imperata cylindrica grows in well lit regularly mown or burnt areas
where there is little competition from taller plants. It prefers loose,
disturbed or sandy soils. Dense masses compete with lower growing plants,
burn readily, and recover vigorously from the rhizomes after mowing or fire.
It does not tolerate shade and ceases abruptly at the edge of rainforest or
other heavy shade." (Swarbrick, 1997; p. 40). In Papua New Guinea, "a coloniser of disturbed land and a weed of plantations and fallow cultivation" (Henty & Pritchard, 1975; p. 42).

"The leaves are easily burnt in dry weather, but the underground rhizome is
undamaged. After a grass fire new growth is started immediately and is
followed by gregarious flowering. Other plants growing with it (such as
tree and shrub seedlings) are frequently killed by a burn or repeated burning so
that open stretches of Imperata cylindrica are often very persistent.
The roots also are highly competitive and exert a depressing effect on other plants" (Gilliland, 1971; pp. 220-221).

Propagation:I. cylindrica may reproduce by seed and rhizomes. Flowering of I. cylindrica is usually initiated by stress, such as burning, cutting or drought. Numerous seeds produced (as many as 3,000 per plant) which can be wind-dispersed over long distances. Santiago (1965) reported that 95 percent can germinate within a week of harvest and seeds can remain viable for at least one year. I. cylindrica also reproduces Vegetatively. Eussen (1980) reported that a single rhizome node could lead to the production of 350 shoots in six weeks and ground cover of 4 square meters in 11 weeks.

Fosberg et al. (1987; p. 45) list I. cylindrica as being present in Saipan, Tinian and Guam and I. conferta as being present in Saipan, Tinian, Rota, Guam, Palau and Yap. Yuncker (1959, p. 64) lists it as being present in Tonga, but it is apparently I. conferta.

Control:

Physical: In small areas, dig and remove all plants and underground stems. Repeat treatments will probably be necessary.

Flattening foliage with rollers or boards can help to suppress I. cylindrica if used in combination with a legume cover crop (Bourgoing and Boutin 1987; Cox and Johnson 1991).

Chemical: Glyphosate is applied typically at a dose rate of 1.8 kg a.e./ha to actively growing foliage of I. cylindrica from where it is absorbed and translocated to the rhizomes, causing death of most of the plant within 2-4 weeks. A little regrowth is almost inevitable and this should be treated with spot applications. Glyphosate can be applied in volume rates ranging from 20 l/ha (using spinning disc sprayers) to 600 l/ha (using hand-held hydraulic sprayers). Glyphosate should be applied 6-8 hours before rain falls and washes it off the weed. Burning several months before treatment enhances uptake of the herbicide.